The purpose of this proposal is to isolate and characterize protein factors which are associated with RNa polymerase (RPase) core during growth and sporulation of Bacillus subtilis and which differ from the sigma factor. The main goal would be to determine the functional roles of these modified cores in transcription. Preliminary investigations have revealed that two proteins found in log phase cells, the ribosomal protein S1 and a newly identified chi factor of 64,000 daltons, can associate with RPase core. Also two factors (delta 1 and delta 2) were found to be associated with RPAse core only during sporulation. Several different approaches will be taken to study the mechanism of polypeptide-RPase core interaction and the functions of these modified cores. They will include an analysis of the mode of association of these factors with the core by dissociation-reassociation techniques, a study of the interaction of modified cores with the sigma factor, a study of the physiological conditions which control the synthesis and relative amounts of these factors, a characterization of the RNA transcripts made by these various forms of RPase, and an analysis of the binding specificity of these modified cores with natural and synthetic DNA templates. One further approach will include the continued use of RNA polymerase mutants which are temperature sensitive only during sporulation as a probe to determine whether sequential synthesis of delta-factors occurs during sporulation. These studies should give us some ideas on how protein factors regulate RPase function during growth and differentiation: whether factors can change the DNA binding specificity of RPase core, whether modified cores actually transcribe different DNA sequences, whether modifications are reversible, whether growth conditions trigger modifications, whether sequential modification of RPase cores can be a mechanism for sequential "turning on" of genes during differentiation.